pub fn string_test() -> ()
{
    let mut str: String = String::from("Hello world!");
    println!("{}", str);
    str = "See you!👋".to_string();
    println!("{}, {}", str, str.len());
    let boolean: bool = false;
    println!("{}", boolean);
    let a: char = 'b';
    println!("{}", a);
}